Custom Links in body to change the text

Hi there. My website is responsive and uses SrbTransLatin in sidebar widget. I wanted to make simple fixed links in body content so mobile users also can change the language (as the widgets are hidden in my WP theme) using those links. I tried to find and use the code of changing the text, but the outcome was not successfull.
What php function may I use in anchor’s “href” attribute to change from Cyrillic to Latin (and vice versa) ?

https://www.ads-software.com/plugins/srbtranslatin/